To achieve high energy conversion efficiency for a semiconductor photovoltaic solar cell, a high output voltage and a high current are required. In order to take advantage of narrow and wide band gap photovoltaic materials, a multijunction photovoltaic solar cell architecture approach has been proposed in which the cell includes a number of stacked photovoltaic solar subcells each with different base layer energy gaps. By connecting the photovoltaic solar cells in a serial fashion with the base layer energy gaps covering different portions of the solar spectrum, enhanced energy conversion efficiency can be achieved.
However, it has proven difficult to provide a path for a photogenerated current to pass from a Group II-VI semiconductor layer to a Group IV semiconductor layer. For example, FIGS. 1A and 1B show that a blocking contact is formed when a p-type ZnTe layer 100 is joined to either light or moderately doped p-type silicon 102 or n-type silicon 104. As is illustrated in FIG. 2, since it is difficult to form stable n-type ZnTe layers, even a highly doped (n++) silicon layer 200 will not form a nonblocking path from a Group II-VI layer 202 (such as ZnTe) to a lightly to moderately doped p-type Group IV layer 204 (such as silicon). Thus, there is a need for a nonblocking path between adjacent subcells where these are formed of a Group IV semiconductor on the one hand and a Group II-VI semiconductor on the other.